Copper base alloy

ABSTRACT

THIS INVENTION RELATES TO NEW AND IMPROVED COPPER BASE ALLOYS CHARACTERIZED BY CONSIDERABLY INCREASED YIELD STRENGTHS COMBINED WITH GOOD DUCTILITY, AND AN ATTRACTIVE SILVERY APPEARANCE ESPECIALLY WHEN POLISHED, SUCH ALLOY COMPRISING THE FOLLOWING CONSTITUENTS IN THE PROPORTIONS SPECIFIED:   PERCENT BY WEIGHT ALUMINUM 1-1.5 MANGANESE 17-22 ZINC 17-22 COPPER 58-60.5 A SMALL AMOUNT OF LEAD, WHICH IS SUFFICIENT TO IMPART MACHINABILITY TO THE ALLOY BUT IS NOT IN EXCESS OF ABOUT 7% BY WEIGHT THEREOF, IS INCORPORATED IN THE ALLOY OF THIS INVENTION IN ANOTHER EMBODIMENT OF THE INVENTION.

"United" States Patent Office U.S. Cl. 75-1575 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to new and improved copper base alloys characterized by considerably increased yield strengths combined with good ductility, and an attractive silvery appearance especially when polished, such alloy comprising the following constituents in the proportions specified:

Percent by weight Aluminum 1-1.5 Manganese 17-22 Zinc 17-22 Copper 555-605 A small amount of lead, which is sufficient to impart machinability to the alloy but is not in excess of about 7% by weight thereof, is incorporated in the alloy of this invention in another embodiment of the invention,

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of our copending U.S. patent application Ser. No. 667,094, filed Sept. 12, 1967, now abandoned.

BACKGROUND TO THE INVENTION (1) Field of the invention This invention relates to new and improved copper base alloys and more particularly to such copper base alloys characterized by the combination of considerably increased yield strength and good ductility, and having an attractive silvery appearance, especially when polished.

(2) Description of the prior art Alloys are known in the prior art which contain 0.15- 2.2% aluminum, -25% zinc, 6-30% manganese and 60-74% copper. Such alloys containing the aforementioned components in amounts within the percentage ranges stated have good ductility, high tensile strength and retain their composition during remelting. Alloys are also known containing to 37.5% zinc, 7 .5-30% manganese, 0.122% aluminum and the balance copper. Such lastmentioned alloys are characterized by high tensile strength and good ductility. Alloys containing 0.25-l% silicon, 55-72% copper, 10-24% zinc, 8-31% manganese, and 0.15-2.0% aluminum are also known in the prior art. Although these last-mentioned alloys are entirely satisfactory for certain purposes, the alloys sutfer from loss of ductility and development of embrittlement due to the addition of the silicon.

SUMMARY OF THE INVENTION In accordance with the present invention, we have found that considerably increased and good yield strengths combined with good ductility and an attractive silvery appearance, especially when polished, are attained in such prior aluminum-manganese-zinc-copper alloys provided Patented Oct. 9, 1973 the alloy is prepared with the constituents present in proportions within the following ranges:

Percent by weight Aluminum 1-1.5 Manganese 17-22 Zinc 17-22 Copper 58-60.5

The l-l.5 percentage range of aluminum in such alloy composition is critical, and the 58-60.5 percentage range of copper in such alloy is also critical, for the reasons hereinafter set forth. The alloys of this invention are free of silicon as a component, and hence do not suffer the loss of ductility and the development of embrittlement attributed to the silicon. Striking increases in yield strength approaching and considerably in excess of were exhibited by alloys of this invention, and good ductility was also shown by the invention alloys. And the attainment of such large increases in yield strength was unexpected and surprising. The properties of yield strength and ductility are of considerable importance to the alloys of this invention for the specific applications for which they are intended or destined, for instance in plumbing, marine and building hardware. Further the attractive silvery appearance of the alloys, especially when polished, renders the alloys well suited for these applications without the requirement of a chrome or other decorative metal plating.

In another embodiment of the invention, a small amount of lead which is sufiicient to impart machinability to the particular alloy is incorporated in or added to the alloys of this invention. By imparting machinability to the alloy, the lead improves or enhances materially the capability of the alloy to be machined. The lead does not substantially adversely affect the mechanical properties of the alloys of this invention and hereinafter set forth so long as the amount of lead utilized in the alloy is not in excess of about 7% by weight, based on the total alloy composition. By machinability as used herein and in the appended claims is meant the capability or ability of the alloy to be machine, for example, shaped, turned, milled or otherwise reduced or worked, by a suitable machine or machines, as for example a casting of the alloy to be machined to specified shape and dimensions.

DETAILED DESCRIPTION OF THE INVENTION The aluminum content of the aluminum-manganesezinc-copper alloys of this invention is critically kept within the range 1-1.5% inclusive for the reasons (1) at an aluminum content significantly below 1%, the considerably increased yield strengths are not attained, and (2) at an aluminum content significantly above 1.5%, alloys of good ductility are no longer obtained. The copper content of such aluminum-manganese-zinc-copper alloys of this invention is critically kept within the range 58- 60.5% inclusive for the reasons (1) with an amount of copper significantly below 58%, alloys of low ductility are obtained, and (2) at an amount of copper significantly in excess of 60.5%, alloys of low yield strength and low tensile strength are obtained. To maintain the improved, good yield strength in the alloys herein, as the aluminum is increased within the 1%-1.5% range, the copper is increased within the 58%60.5% range. As the aluminum is decreased within the 1%-1.5% range, the copper is decreased within the 58%60.5% range to maintain the improved, good yield strength of the alloy. To maintain good elongation, i.e., ductility, in the alloys, as the aluminum is increased within the 1%-1.5% range, the copper is increased within the 58%60.5% range. As the aluminum is decreased within the 1%-1.5% range, the copper is decreased within the 58%60.5% range to maintain good ductility. The lower limit of 17% manganese assures obtained an attractive silvery appearance of the alloy, especially when polished. With zinc present in the alloy in amounts much in excess of 22%, fuming of the zinc may occur resulting in undesirable changes in the composition of the alloy and which may be undesirable with respect to the health of workers in the immediate vicinity.

The percentages of the constituents of the alloys of this invention usually total 100 for each alloy, exclusive of any incidental impurities which may be present, and are based on the total alloy composition.

The aluminum-manganese-zinc-copper alloys of this invention are characterized by the following mechanical properties in the sand cast form:

Yield strength Minimum 30,000 pounds 1 per square inch. Elongation Minimum 20% in 2 inches. Tensile strength Minimum 60,000 pounds per square inch'.

The aluminum-manganese-zinc-copper alloys herein have a liquidus below 1850 F. and usually in the range of 1550 F.1600 F. This relatively low melting feature as contrasted with the much higher melting temperature of certain nickel-silver alloys facilitates casting of such alloys. Further, aluminum-manganese-zinc-copper alloys herein exhibit flexibility or versatility in casting, are readily cast by sand, die or permanent mold casting, and show good resistance to corrosion by the atmosphere, by citrus juices and by sea water.

Incidental impurities which can be present in the alloys herein are, for example, iron, lead, tin, antimony and arsenic. The presence of the lead as an incidental impurity in the alloy is to be differentiated from the presence of the lead as a constituent of the alloy to improve the machinability of the alloy.

The following examples further illustrate the invention. The comparative tests of the examples were carried out on sand cast test bars (A.S.T.M. specification B208-58. FIGS. 1 and 5) of the alloy compositions specified in the following table. The following results were obtained:

Alloy composition, Yield percent by weight strength, Elongation,

lbs. per percent in Example Cu Zn Al Mn square inch 2 inches The test results of the table show the considerable improvement in yield strength provided by the alloy compositions of the present invention. Thus the alloy composition of Example 7 of the foregoing table containing aluminum within the 1-1.5% range exhibited greater than a 100% increase in yield strength over that of the alloy composition of Example 21 containing 0.8% aluminum; and the alloy compositions of Examples 4 and 14 also containing aluminum within the 1-1.5%

range showed close to a increase in yield strength over that of the alloy composition of Example 21. The alloy composition of Examples 8, 9, 13 and 16 containing aluminum within the 1-l.5% range showed yield strengths which were also a considerable improvement those of the alloy compositions of Examples 5, ll, 12, 15 and l722 which contained aluminum in amounts below 1%; yield strengths which were a considerable improvement over that of the alloy composition of Example 24 free of aluminum as a component; and yield strength which were also a considerable improvement over that of the alloy composition of Example 25 containing aluminum in excess of 1.5%. The alloy compositions of Examples 1, 2 and 3 of the foregoing table having a copper content below 58% showed low elongation, i.e. ductility. The alloy compositions of Examples 6, 10 and 23 of the table having an aluminum content in excess of 1.5% also exhibited low elongation. The alloy compositions of Examples 5, 11, 12, 15 and l7-22 of the table having an aluminum content below 1% all showed low yield strengths. The invention alloy compositions of Examples 4, 7, 8, 9, l3, l4, and 16 were of an attractive silvery luster in appearance.

In another embodiment of the invention, it was found that nickel as a component of the copper base alloy together with the copper, aluminum, manganese and zinc resulted in an alloy not only of good resistance to corrosion by the atmosphere, citrus juices and sea water but also of considerably improved resistance to corrosion by salt spray. The nickel is employed in the alloy in a minimum of 3% and up to a maximum of 6% inclusive based on the weight of the total 5 component alloy, percentages being by weight. The minimum of 3% of the nickel is required for significant improvement of the alloy to resistance to corrosion by salt spray, and there is no significant improvement of the alloy in resistance to salt spray corrosion with an amount of nickel much in excess of 6%. Such copper base alloys of this embodiment of the invention comprise the following constituents in the and the balance copper, the sum of the copper plus nickel being in the range of 59 to 61.5 percent by weight.

Such alummum-manganese-zinc-nickel-copper alloys are also characterized by good yield strength, good ductility, an attractive silvery appearance especially when polished, and high tensile strength, with such properties being similarly good as the corresponding properties of the quaternary alloys. The aluminum-manganese-zincnickel-copper alloys are also characterized by melting at a relatively low temperature and having a liquidus below 1850 F.

When lead is a constituent of the alloys of this invention to improve its machinabilty, the lead is preferably utilized in amount, by weight, from about 0.5 %2%, most preferably about 1%1.5%, based on the total alloy composition.

The aluminum-manganese-zinc-copper alloys of this invention also containing lead as a constituent to improve machinabilit contain the constituents in proportions within the following ranges:

Percent by weight Aluminum 1 to 1.5 Manganese 17 to 22 Zinc 17 to 22 Copper 54 to 60 Lead About 0.5 to 7 When the lead is present in a preferred amount, the aluminum-manganese-zinc-copper alloys herein also containing the lead contain the constituents in proportions preferably within the following ranges:

Percent by weight Aluminum 1 to 1.5 Manganese 17 to 22 Zinc 17 to 22 Copper 57 to 59.5 Lead About 0.5 to 2 The aluminum-manganese-zinc-nickelcopper alloys of this invention also containing lead as a constituent to improve machinability contain the constituents in proportions within the following ranges:

Percent by weight Aluminum 1 to 1.5 Manganese 17 to 22 Zinc 17 to 22 Nickel 3 to 6 Lead About 0.5 to 7 and the balance copper, the sum of the copper plus the nickel being in the range of 55 to 61 percent by weight.

When the lead is present in a preferred amount, the aluminum-manganese-zinc-nickel-copper alloys herein also containing the lead contain the constituents in proand the balance copper, the sum of the copper plus nickel being in the range of 58 to 60.5 percent by weight.

The aluminum-manganese-zinc-copper alloys of this invention are prepared by first melting the copper and then heating the melt until it reaches a sufficiently high temperature to avoid freezing when the other alloying components are subsequently added. The manganese is then added in small portions until all of the manganese has dissolved in the molten copper. A small amount of borax is then preferably added to remove the oxide on the melt surface. The zinc is then added and the molten mixture is stirred to obtain a uniform melt. Finally the aluminum is added in small pieces placed on the melt surface, and the aluminum is allowed to dissolve in the melt Without stirring. The melt is then stirred, followed by permitting the melt to stand for a short time, say a few minutes, to enable entrained oxides to reach the surface of the melt, and the melt is then skimmed and poured into the mold.

The aluminum manganese zinc nickel copper alloys herein are prepared by the same procedure as utilized in preparing the aluminum-manganese-zinc copper alloys and above described, except that in preparing such nickelcontaining alloys the nickel is melted together with the copper. When lead is a constituent of an alloy of this invention the lead can be incorporated in the alloy by first preparing the alloy minus the lead by the procedure previously disclosed herein and then adding the lead in molten or solid form to the alloy melt.

Crucibles or vessels fabricated of any suitable refractory material, for example clay-graphite or silicon carbide, and well known to the art are utilizable for preparing and handling the alloys herein.

The alloys of this invention containing the lead as a constituent to improve machinability are also characterized by good yield strength, good ductility, an attractive silvery appearance especially when polished, and high tensile strength, with such properties being similarly good as the corresponding properties of the aluminum-manganese-zinc-copper alloys herein.

The alloys of this invention are eminently well suited for use in plumbing accessories and fixtures, for instance faucets, valve knobs, shower heads and drain covers, marine hardware, for instance cleats and chocks, and building hardware both in the interior and exterior of the building, for instance door knobs and escutcheon plates. While the alloys are utilizable without the requirement of of a chrome or other decorative metal plating thereover due to their attractive silver color especially when polished, the alloys can of course be plated with chrome or other decorative metal if this is desired. In the event, should the chrome or other decorative metal plating wear off, the exposed metal will still be an attractive and decorative silvery surface.

What is claimed is:

1. A copper base alloy characterized by a silvery appearance appearance especially when polished and consisting essentially of the following ingredients in the proportions specified:

Percent by weight Aluminum 1-1.5 Manganese 17-22 Zinc 17-22 Copper 58-60.5

the alloy having the following characteristics in the sand cast form:

Tensile strength p.s.i. Minimum 60,000 Yield strength p.s.i... Minimum 30,000 Elongation percent in 2 inches" Minimum 20 said alloy further being characterized by having a liquidus of below 1850 F., said alloy being free of silicon as a component.

2. The alloy of claim 1 wherein lead is an additional ingredient thereof, the lead being present in a small amount suflicient to impart machinability to the alloy but not in excess of about 7% by weight based on total alloy composition.

3. The alloy of claim 2 wherein the lead is present in an amount within the range from about 0.5%-2% by weight based on the total alloy composition.

References Cited UNITED STATES PATENTS 2,400,234 5 1946- Hudson -157 .5

2,445,868 7/1948 Berwick 75 -1575 2,479,595 8/1949 Anderson et al. 75157.5

2,479,596 8/ 1949 Anderson et al 75-157.5

FOREIGN PATENTS 918,446 10/ 1946 France 75157.5

OTHER REFERENCES German publication-Auslegeschrift No. 1,183,692, December 1964, 3 pages.

CHARLES N. LOVELL, Primary Examiner 2 g 7 UNITED STATES PATENT OFFICE 1 CERTIFICATE OF CORRECTEON Patent N 3,764,306 Dated October 9 197% Edward A. Blythe, Allan S. Gelb and Donald L. LaVelle It is certified that error appears in the above-identified" patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 40, "machine" should read --machined--; .last line, "obtained" should read --obtaining--. Column 4, line 5, "also a considerable" should be deleted and --an appreciable-- substituted therefor. Column 6, line 24, "appearance" (second occurrence) should be deleted.

Signed and sealed this 2nd day of April 197M.

(SEAL) Attest:

EDWARD I LFLETCHERJR 0. MARSHALL DANN Attesting; Officer Commissioner of Patents 

